# ideal_age_example module reference¶

A tracer package of ideal age tracers.

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## Data Types¶

 ideal_age_tracer_cs The control structure for the ideal_age_tracer package.

## Functions/Subroutines¶

 register_ideal_age_tracer() Register the ideal age tracer fields to be used with MOM. initialize_ideal_age_tracer() Sets the ideal age traces to their initial values and sets up the tracer output. ideal_age_tracer_column_physics() Applies diapycnal diffusion, aging and regeneration at the surface to the ideal age tracers. ideal_age_stock() Calculates the mass-weighted integral of all tracer stocks, returning the number of stocks it has calculated. ideal_age_tracer_surface_state() This subroutine extracts the surface fields from this tracer package that are to be shared with the atmosphere in coupled configurations. ideal_age_example_end() Deallocate any memory associated with this tracer package.

## Detailed Description¶

Originally by Robert Hallberg, 2002.

This file contains an example of the code that is needed to set up and use a set (in this case two) of dynamically passive tracers for diagnostic purposes. The tracers here are an ideal age tracer that ages at a rate of 1/year once it is isolated from the surface, and a vintage tracer, whose surface concentration grows exponen- with time with a 30-year timescale (similar to CFCs).

## Type Documentation¶

type ideal_age_example/ideal_age_tracer_cs

The control structure for the ideal_age_tracer package.

Type fields
• % ntr [integer] :: The number of tracers that are actually used.

• % coupled_tracers [logical] :: These tracers are not offered to the coupler.

• % nkml [integer] :: The number of layers in the mixed layer. The ideal.

• % ic_file [character (len=200)] :: The file in which the age-tracer initial values can be found, or an empty string for internal initialization.

• % z_ic_file [logical] :: If true, the IC_file is in Z-space. The default is false.

• % time [type(time_type),pointer] :: A pointer to the ocean model’s clock.

• % tr_reg [type(tracer_registry_type),pointer] :: A pointer to the tracer registry.

• % tr [real(:,:,:,:),pointer] :: The array of tracers used in this package, in g m-3?

• % ic_val [real( ntr_max )] :: The (uniform) initial condition value.

• % young_val [real( ntr_max )] :: The value assigned to tr at the surface.

• % land_val [real( ntr_max )] :: The value of tr used where land is masked out.

• % sfc_growth_rate [real( ntr_max )] :: The exponential growth rate for the surface value [year-1].

• % tracer_start_year [real( ntr_max )] :: The year in which tracers start aging, or at which the surface value equals young_val, in years.

• % tracers_may_reinit [logical] :: If true, these tracers be set up via the initialization code if they are not found in the restart files.

• % tracer_ages [logical( ntr_max )] :: Indicates whether each tracer ages.

• % ind_tr [integer( ntr_max )] :: Indices returned by atmos_ocn_coupler_flux if it is used and the surface tracer concentrations are to be provided to the coupler.

• % diag [type(diag_ctrl),pointer] :: A structure that is used to regulate the timing of diagnostic output.

• % restart_csp [type(mom_restart_cs),pointer] :: A pointer to the restart controls structure.

• % tr_desc [type(vardesc)( ntr_max )] :: Descriptions and metadata for the tracers.

## Function/Subroutine Documentation¶

function ideal_age_example/register_ideal_age_tracer(HI, GV, param_file, CS, tr_Reg, restart_CS) [logical]

Register the ideal age tracer fields to be used with MOM.

Parameters
• hi :: [in] A horizontal index type structure

• gv :: [in] The ocean’s vertical grid structure

• param_file :: [in] A structure to parse for run-time parameters

• cs :: The control structure returned by a previous call to register_ideal_age_tracer.

• tr_reg :: A pointer that is set to point to the control structure for the tracer advection and diffusion module

• restart_cs :: A pointer to the restart control structure

Call to
subroutine ideal_age_example/initialize_ideal_age_tracer(restart, day, G, GV, US, h, diag, OBC, CS, sponge_CSp)

Sets the ideal age traces to their initial values and sets up the tracer output.

Parameters
• restart :: [in] .true. if the fields have already been read from a restart file.

• day :: [in] Time of the start of the run.

• g :: [in] The ocean’s grid structure

• gv :: [in] The ocean’s vertical grid structure

• us :: [in] A dimensional unit scaling type

• h :: [in] Layer thicknesses [H ~> m or kg m-2]

• diag :: [in] A structure that is used to regulate diagnostic output.

• obc :: This open boundary condition type specifies whether, where, and what open boundary conditions are used.

• cs :: The control structure returned by a previous call to register_ideal_age_tracer.

• sponge_csp :: Pointer to the control structure for the sponges.

Call to
subroutine ideal_age_example/ideal_age_tracer_column_physics(h_old, h_new, ea, eb, fluxes, dt, G, GV, US, CS, evap_CFL_limit, minimum_forcing_depth)

Applies diapycnal diffusion, aging and regeneration at the surface to the ideal age tracers.

Parameters
• g :: [in] The ocean’s grid structure

• gv :: [in] The ocean’s vertical grid structure

• h_old :: [in] Layer thickness before entrainment [H ~> m or kg m-2].

• h_new :: [in] Layer thickness after entrainment [H ~> m or kg m-2].

• ea :: [in] an array to which the amount of fluid entrained

• eb :: [in] an array to which the amount of fluid entrained

• fluxes :: [in] A structure containing pointers to thermodynamic and tracer forcing fields. Unused fields have NULL ptrs.

• dt :: [in] The amount of time covered by this call [T ~> s]

• us :: [in] A dimensional unit scaling type

• cs :: The control structure returned by a previous call to register_ideal_age_tracer.

• evap_cfl_limit :: [in] Limit on the fraction of the water that can be fluxed out of the top layer in a timestep [nondim]

• minimum_forcing_depth :: [in] The smallest depth over which fluxes can be applied [H ~> m or kg m-2]

Call to
function ideal_age_example/ideal_age_stock(h, stocks, G, GV, CS, names, units, stock_index) [integer]

Calculates the mass-weighted integral of all tracer stocks, returning the number of stocks it has calculated. If stock_index is present, only the stock corresponding to that coded index is found.

Parameters
• g :: [in] The ocean’s grid structure

• gv :: [in] The ocean’s vertical grid structure

• h :: [in] Layer thicknesses [H ~> m or kg m-2]

• stocks :: [out] the mass-weighted integrated amount of each tracer, in kg times concentration units [kg conc].

• cs :: The control structure returned by a previous call to register_ideal_age_tracer.

• names :: [out] the names of the stocks calculated.

• units :: [out] the units of the stocks calculated.

• stock_index :: [in] the coded index of a specific stock being sought.

Return

undefined :: The number of stocks calculated here.

Call to

mom_io::query_vardesc

Called from

mom_tracer_flow_control::call_tracer_stocks

subroutine ideal_age_example/ideal_age_tracer_surface_state(sfc_state, h, G, GV, CS)

This subroutine extracts the surface fields from this tracer package that are to be shared with the atmosphere in coupled configurations. This particular tracer package does not report anything back to the coupler.

Parameters
• g :: [in] The ocean’s grid structure.

• gv :: [in] The ocean’s vertical grid structure

• sfc_state :: [inout] A structure containing fields that describe the surface state of the ocean.

• h :: [in] Layer thickness [H ~> m or kg m-2].

• cs :: The control structure returned by a previous call to register_ideal_age_tracer.

Call to

mom_coupler_types::set_coupler_type_data

subroutine ideal_age_example/ideal_age_example_end(CS)

Deallocate any memory associated with this tracer package.

Parameters

cs :: The control structure returned by a previous call to register_ideal_age_tracer.